Conventionally, a cellular telephone device as a mobile terminal device has been known, which includes a first body, a second body, and a connecting portion connecting the first body and the second body, and which is configured so as to be capable of transitioning to an opened state and a closed state via the connecting portion depending on the usage aspects. A cellular telephone device of such a folder type has a communication function to perform communication externally via an antenna.
For example, Patent Document 1 proposes a cellular telephone device, in which an antenna element disposed in the first body can be utilized as an antenna in the closed state, and in which one of a first conductive portion disposed in the first body and a second conductive portion disposed in the second body can be utilized as an antenna in the opened state, by feeding power to one of the first conductive portion and the second conductive portion and by grounding the other one (in a ground state).
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2007-104468